In agricultural areas where fields are irrigated by running water into furrows, erosion of the soil is a major problem. While furrow irrigation has significant advantages including water saving and less costly equipment, especially as compared with overhead sprinklers, it also has some disadvantages. In particular, furrow or ditch irrigation causes significant soil erosion as the water running along the furrow washes away soil. In some areas, erosion of topsoil can amount to between 2.8 and 28 tons per acre during a 24 hour watering interval.
In addition, this form of irrigation can remove valuable pesticides and fertilizers which become pollutants in the waterways to which they run, and the soil itself can become less porous, and therefore less able to accept the irrigation water and convey it to plant roots, as fine clay particles settle out of the water and clog soil pores.
It has been found that certain polyacrylamides (PAMs) greatly alleviate these problems and make furrow irrigation a useful and much less destructive irrigation technique, extending the useful life of many acres of farmland. PAMs are long-chain polymers, also used to clean waste water, which reduce the amount of soil carried by the irrigation water and reduces the negative effect of the erosion on soil porosity. Although the mechanism by which this is accomplished is not fully understood, its effectiveness is widely acknowledged.
PAMs are employed in furrow irrigation by adding selected quantities of the substance in a powder-like form to the irrigation water as the water is dispensed or flowed into the field. Unfortunately, before the material is added to the irrigation water, it is highly sensitive to moisture, particularly moisture in the air, i.e., humidity. When the dry polymer is exposed to moisture, it tends to become sticky and agglomerates. As the amount of moisture increases, the substance becomes increasingly sticky and no longer flows as a powder. Any attempt to simply dispense the PAM through a tube under humid conditions results in the tube being blocked by agglomerated PAM in a short interval of time.
This becomes important because the PAM must be dispensed over and adjacent to the surface of the irrigation water in order to prevent it from being blown away and lost, a dispenser being held as close as one inch to, or as far away as one foot from, the water surface. The proximity of the dispenser to the water creates humidity where it is least wanted, in the dispensing tube.